From 8d4e29eb355aa5c43ffe41001404cc0a49640188 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Wed, 4 Nov 2020 10:31:28 +0300
Subject: [PATCH] Support loading index-only data in gfx::mesh

---
 libs/gfx/include/psemek/gfx/mesh.hpp | 52 ++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/libs/gfx/include/psemek/gfx/mesh.hpp b/libs/gfx/include/psemek/gfx/mesh.hpp
index c1e21f8d..1291f533 100644
--- a/libs/gfx/include/psemek/gfx/mesh.hpp
+++ b/libs/gfx/include/psemek/gfx/mesh.hpp
@@ -150,6 +150,20 @@ namespace psemek::gfx
 		template <typename Vertex, typename Index, std::size_t N>
 		void load(std::vector<Vertex> const & vertices, std::vector<geom::simplex<Index, N>> const & simplices, GLenum usage = gl::STREAM_DRAW);
 
+		// Index-only vertex data
+
+		template <typename Index>
+		void load_index(Index const * indices, std::size_t index_count, GLenum primitive_type, GLenum usage = gl::STREAM_DRAW);
+
+		template <typename Index>
+		void load_index(std::vector<Index> const & indices, GLenum primitive_type, GLenum usage = gl::STREAM_DRAW);
+
+		template <typename Index, std::size_t N>
+		void load_index(geom::simplex<Index, N> const * simplices, std::size_t simplex_count, GLenum usage = gl::STREAM_DRAW);
+
+		template <typename Index, std::size_t N>
+		void load_index(std::vector<geom::simplex<Index, N>> const & simplices, GLenum usage = gl::STREAM_DRAW);
+
 		// Instance data
 
 		template <typename Instance>
@@ -291,6 +305,44 @@ namespace psemek::gfx
 		load(vertices.data(), vertices.size(), simplices.data(), simplices.size(), usage);
 	}
 
+	template <typename Index>
+	void mesh::load_index(Index const * indices, std::size_t index_count, GLenum primitive_type, GLenum usage)
+	{
+		if (auto n = detail::get_primitive_type_vertex_count(primitive_type); n)
+			assert((index_count % (*n)) == 0);
+
+		if (!index_buffer_)
+		{
+			index_buffer_ = buffer{};
+			array_.bind();
+			gl::BindBuffer(gl::ELEMENT_ARRAY_BUFFER, index_buffer_.id());
+		}
+		index_buffer_.load(indices, index_count, usage);
+		info_.index_count_ = index_count;
+		info_.indexed_ = true;
+		info_.primitive_type_ = primitive_type;
+		info_.index_type_ = detail::index_type_to_gl_enum_v<Index>;
+	}
+
+	template <typename Index>
+	void mesh::load_index(std::vector<Index> const & indices, GLenum primitive_type, GLenum usage)
+	{
+		load_index(indices.data(), indices.size(), primitive_type, usage);
+	}
+
+	template <typename Index, std::size_t N>
+	void mesh::load_index(geom::simplex<Index, N> const * simplices, std::size_t simplex_count, GLenum usage)
+	{
+		static_assert(sizeof(Index) * (N + 1) == sizeof(simplices[0]));
+		load_index(reinterpret_cast<Index const *>(simplices), simplex_count, detail::get_primitive_type<N>(), usage);
+	}
+
+	template <typename Index, std::size_t N>
+	void mesh::load_index(std::vector<geom::simplex<Index, N>> const & simplices, GLenum usage)
+	{
+		load_index(simplices.data(), simplices.size(), usage);
+	}
+
 	template <typename Instance>
 	void mesh::load_instance(Instance const * instances, std::size_t count, GLenum usage)
 	{